(A, B) IP was subjected to pull down either CD74 or CD44. The blots were probed with either mouse anti-CD74 or anti-CD44 antibodies. The antibody (Ab) heavy and light chain bands are indicated so that Ab heavy and light chain fragments can be observed at approximately 55 and 25 kDa, respectively. (C, D) Co-IP was applied to study the interaction of CD74/CD44 and CD44/CD74. The Co-IP of CD74/CD44 confirmed that all CD44 isoforms, including CD44s and CD44, interact with CD74. However, Co-IP of CD44/CD74 confirmed that only p41 of CD74 interacts with CD44. Figures depict representative samples from duplicate experiments displayed as composites of multiple co-immunoprecipitation.